Blends of cellulosic and polypivalolactone staple fibers



United States Patent 3,379,001 BLENDS 0F CELLULOSIC AND PQLYPiVALO- LACTGNIE STAPLE FIBERS Tod W. Campbell, Waynesboro, Va., and Fred Witliarn Knobloch, Hociressin, DeL, assignors to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware No Drawing. Filed Apr. 9, 1965, Ser. No. 447,031 9 illaims. (Cl. 57140) ABSTRACT OF THE DISCLOSURE Blends of from about 20 to 95% by weight of cellulosic staple fibers and from about to 80% of polypivalolactone staple fibers exhibit high compressional recovery properties and fabrics made of the blends have good wash-wear performance.

This invention relates to novel cellulosic fiber blends.

Cellulosic fibers such as cotton and rayon are abundant and inexpensive, and they are useful for making a wide variety of articles. Garments made from them are considered comfortable and aesthetically pleasing when properly cared for. However, cellulosic fibers are known to have poor recovery properties, such as inferior recovery from compression and poor ability to recover from wrinkling in fabric form. Such deficiencies have imposed limitations on the use of cellulosic fibers for certain forms of stuffing materials, for high performance wash-wear garments requiring only minimum care, and for carpets and other articles requiring good recovery properties.

It has now been found that a blend of cellulosic fibers with as little as 5% of polypivalolactone staple fibers exhibits markedly improved recovery properties. Blends of cellulosic fibers with at least about polypivalolactone staple fibers give striking results; such blends have higher recovery from compression, and fabrics made of the blends have better wash-wear performance, than cellulosic fiber blends containing 65% polyethylene terephthalate fiber, Even more outstanding results are obtained with blends containing about equal parts of cellulosic fibers and polypivalolactone fibers. Still higher proportions of the polypivalolactone may be used if desired, of course.

The cellulosic fiber blends of this invention are particularly well adapted for the preparation of staple yarns to be used in making fabrics for wash-wear garments. Great efforts have been expended on the development of such garments, requiring only minimum care. The goal has been a garment which presents and retains a neat appearance during wearing, without the development of Wrinkles; and which can then be laundered in hot water, dried on the line, and still present a neat appearance when worn again without the necessity of pressing to remove wrinkles. Blends containing about 35% cotton and 65 polyethylene terephthalate fiber have achieved commercial importance, since they provide considerable improvement over 100% cotton fabrics in wash-wear performance. However, garments made from blends of cotton with from about 15% to about 50% polypivalolactone staple fiber exhibit superior wash-wear performance and also have high aesthetic appeal because they contain such a high proportion of cotton.

For optimum wash-wear performance while still retaining benefits of the cellulosic fibers, such as resistance to the build-up of static electricity as contrasted with the fibers of synthetic polymer used alone, blends containing up to 80% polypivalolactone fiber with cellulosic fiber may be employed. It is preferred, however, that the blends contain at least about cellulosic fiber when 3,379,001 Patented Apr. 23, 1%68 ice it is desired to incorporate in the fabric to a considerable extent the aesthetics of cellulosic fibers.

Any of the various conventional methods for mixing the cellulosic fibers with fibers of synthetic polymers to form a blend and working up the fiber blend to form a fabric may be employed, Standard textile equipment may be used for processing cellulosic staple blends into staple yarns, and weaving or knitting the yarns into fabrics. As is well known, the properties and performance of a fabric are dependent upon its construction; but for any given fabric construction, the novel cellulosic fiber/polypivalolactone staple fiber blends of the invention yield markedly superior results to those obtained with cellulosic fibers used alone.

As used herein, the term cellulosic fiber refers to any fiber composed substantially of cellulose. Included are both natural cellulosic fibers such as cotton, fiax, hemp, etc. and rayon, or other fibers of regenerated cellulose, whether linear or cross-linked. More specifically, the term cellulose is defined as a polymer composed of anhydroglucose units linked at the 1 and 4 positions through glucosidic bonds with the beta configuration, wherein fewer than one-half of the anhydroglucose units are chemically substituted. Thus, the term does not comprehend cellulose acetate or other derivatives of cellulose in which one or more hydroxyl groups on most or all of the anhydroglucose units are esterified.

As used herein, the term plypivalolactone refers to a linear condensation polyester comprised essentially of recurring ester structural units of the formula Alternative names for the polyester include poly(hydroxypivalic acid), poly (2,2-dirnethylhydracrylic acid), and poly(oxycarbonyl-l, l-dimethyldimethylene). The polyester is readily prepared by the polymerization of hydroxypivalic acid or its esters as disclosed by Alderson in his US. Patent 2,658,055; or by the polymerization of pivalolactone, the intramolecular ester of hydroxypivalic acid, as disclosed by Reynolds and Vickers in their British Patent 766,347. In a typical procedure, 25 g. of pivalolactone is added to a refluxing mixture of 250 ml. of n-h-exane, 2.5 ml. of ethyl alcohol, 0.25 g. of triethylenediamine, 0.025 g. of 2,2-bis(4-hydroxyphenyl) propane and 0.075 g. of finely divided TiO Refiuxing is continued, with stirring, for 4 hours, during which time the delustered polypivalolactone polymer precipitates from the boiling mixture. The solid polymer is subsequently separated by filtration from the hexane solvent. Minor modifications of the polypivalolactone with copolyrneric components are also comprehended. For example, 2,2-diethylpropiolactone, 2,2-bis(chloromethyl)propiolactone, or other lactones or hydroxyacids may be employed as copolymeric modifiers in amounts ranging up to about 25 mol percent, preferably 1 to about 10 mol percent; or various thermoplastic materials such as other polyesters or polyamides may be incorporated in the molten polypivalolactone in amounts up to about 10% by weight.

The polypivalolactone fiber blended with the cellulosic fiber should be oriented and possess a high degree of polymerization as characterized by an inherent viscosity of at least about 0.75, measured at 30 C. in solution in trifiuoroacetic acid at a concentration of 0.5 gram of polymer per ml. of solution. The polypivalolactone fibers are formed from the polymer by conventional melt-spinning techniques, usually at a spinning temperature in the range of about 250-290 C., with extrusion of the polypivalolactone filaments through capillary orifices in a spinneret and quenching with a current of air or other inert gas, or by passing the extruded filaments into an inert liquid such as water. The filaments may be oriented simply by taking them up on a forwarding roll or windup roll at a thigh spin-stretch factor, i.e. with a ratio of spinning speed at windup to the jet speed of the polymer stream issuing from the capillary orifice suflicient to orient the filaments to the desired extent; or a separate orientation step may be employed, in which the filaments are drawn at a ratio of 1.1 to 5x. The oriented olypivalolactone filaments are usually crimped and are then cut to staple fibers of the desired length. If desired, the filaments may be set or relaxed at a temperature in the range of about 125-200" C., either before or after crimping.

As used herein, the term blend refers to an intimate mixture formed of loose staple fibers composed of different polymers, the fibers being intermingled in substantially random manner.

The novel staple fiber blend of the invention may also contain staple fibers composed of polyamides, polyacrylonitrile, polyurethane, or other staple fibers so long as at least the minimum percentages of cellulosic fiber and polypivalolactone are present as described above, so that the percentages of all the staple fibers in the blend total 100%. Multi-component blends are contemplated. For example, excellent poplins, sharkskins, and twills may be prepared using 40% polypivalolactone staple fibers, 30% cotton, 20% rayon staple fibers, and nylon staple fibers.

The following examples are appended to illustrate the invention, although they are not intended to be limitative.

Example 1 Polypivalolactone having an inherent viscosity of 1.6 and containing 0.3 weight percent titanium dioxide is melt extruded at 276 C. from a spinneret containing orifices, each 0.009 inch (0.023 cm.) in diameter. The extruded filaments are passed through a vertical waterquench tube continuously fed by water maintained at 11 from a cylindrical pan surmounting the tube. The filaments are passed through a convergence guide and the yarn so formed is taken up by a roll at 800 y.p.m. (730 meters per min.) and is then passed to draw roll at 900 y.p.m. (822 m.p.m.) for a draw ratio of 1.12 after which the yarn is wound up. The drawn yarn has a denier of 65. The inherent viscosity of the polymer comprising the yarn is 1.5. The yarn is plied (30 ends) and the plied yarn is then heated by passing it twice around an 8-inch (20.3 cm.) roll heated to 175 C. and operated at a peripheral speed of 60 y.p.m. (55 m.p.m.) the contact time being 1.3 seconds. The plied yarn is padded with a 5% aqueous solution of anionic textile finishing agent and a tow sheet of plied yarns is formed and fed into a stufi'er box crimper and crimped (approximately 8 crimps per inch or about 3 crimps per cm.). The crimped tow is cut to give 1.5 inch (3.81 cm.) staple fibers. The filaments in the crimped tow have a tenacity of 4.7 g.p.d., an elongation of 90%, a modulus of 24 g.p.d., a work recovery of 72% at 5% elongation, and a tensile recovery of 88% at 5% elongation.

Fiber blends are prepared comprising, respectively, 50% and 65% by weight of the olypivalolactone staple fibers and 50% and 35% by weight of combed El Paso cotton (middling grade). It is observed that 50% of the cotton fibers are 1 /8 inches (2.86 cm.) in length or longer. Other blends are prepared comprising 50% and 65% by weight of the olypivalolactone staple fibers and 50% and 35% by weight of standard, 1.5 denier rayon staple fibers having a cut length of 1% inches (3.97 cm.) (standard Avisco XL produced by the American Viscose Corporation as Style 2301).

Samples of the staple fibers are shaped by hand into staple pellets and subjected to the standard Busse compressional recovery test. The Busse compressional recovery test measures the ability of a pellet or plug of staple fibers to recover from compressional forces and is expressed in percent. The apparatus used in the Busse test is described in Textile Research Journal, 23, 84 (1953). The test is performed at 65% relativ humidity and at 70 F. A tuft of staple fibers weighing 0.3 gram is taken from a sliver or batt and placed in a metal cylinder which is 0.8 square inch in area (5.16 crn The tuft of staple is formed into a loose pellet by compressing it with a light wooden rod at approximately 0.2 p.s.i. (14 g./cm. The initial height of the loose pellet is then measured under this load. The wooden rod is then replaced with a steel rod and a loading force of 10,000 p.s.i. (703 kg./cm. is applied to the pellet for one minute. This compressed pellet of fiber is then removed from the cylinder and allowed to recover for 24 hours. The recovery in percent is calculated from the ratio of the recovered pellet height to the initial pellet height. Because of the removal of the rod before the final measurement, the recovery may be greater in some cases than the initial height.

The results obtained in the Busse compressional recovery test with the various staple blends, together with the results for control samples of cotton and 100% rayon fibers, are shown in Table 1.

TABLE 1.BUSSE COMPRESSIONAL RECOVERY TEST [Blends of cellulosic fibers with polypivalolactone staple fibers] Busse Recovery Vlaues Amount of Polypivalolactone Fiber in Blend, Percent Cotton, Rayon,

Percent Percent 50 52 35 G5 71 46 None (100% cellulosic fiber)... 21 15 Example 2 A quantity of the crimped tow of Example 1 is heated for five hours at C., after which it is cut to give 1.5 inch (3.81 cm.) staple fibers. The filaments in the crimped tow have a tenacity of 3.0 g.p.d., an elongation of 92%, a modulus of 25 g.p.d., a work recovery of 84% at 5% elongation, and a tensile recovery of 94% at 5% elongation. A fiber blend is prepared comprising 50% by weight of the heat-set polypivalolactone staple fibers and 50% by weight of the cotton fibers employed in Example 1. A pellet of this staple blend subjected to the standard Busse compressional recovery test exhibits a recovery of 102%.

Another fiber blend is prepared comprising 50% by Weight of the heat-set polypivalolactone staple fibers and 50% by weight of the rayon fibers employed in Example 1. A recovery value of 42% is obtained from a pellet of this staple blend subjected to the standard Busse compressional recovery test. A blend of 65% of the heat-set polypivalolactone staple fibers and 35% by weight of the rayon fibers, when subjected to the Busse test, exhibits a recovery of 58%.

Refiuifable pillows and durable carpets exhibiting good recovery from compression are prepared from the blends of cellulosic fibers with polypivalolactone fiber in the above example.

Even at low levels of polyester fiber content the Busse recovery value of cotton is markedly improved by blending with polypivalolactone fiber, as shown by the followlng example.

Example 3 Fiber blends of the cotton fibers of Example 1 with varying amounts of the polypivalolactone staple fibers of Example 1 (crimped but not heat set) are prepared and subjected to the standard Busse compressional recovery test. Fiber blends of the same cotton fibers with the crimped, heat-set polypivalolacton staple fibers of Ex-' ample 2 are prepared in the same proportions and the Busse recovery values are measured. The results are shown in Table 2.

TABLE .L-BLENDS OF COTTON FIBERS IVITI'I SMALL QUANTITIES OF POLYPIVALOLAOTONE STAPLE FIBERS Weight Percent Busse Recovery Values Polypivalolactone in Blend Unheated Heat-Set Polypivalolaetone Polypivalolactone Fiber, Percent Fiber, Percent Example 4 Molten polypivalolactone having an inherent viscosity of 1.54 and containing 0.3 weight percent titanium dioxide and 0.1 weight percent 2,2-bis(4-hydroxyphenyl) propane is extruded at 284 C. from a spinneret having 30 orifices, each 0.009 inch (0.0229 cm.) in diameter. The extruded filaments are passed through a vertical water-quench tube continuously fed by cold water from a cylindrical pan surmounting the tube. The filaments are passed through a convergence guide and the yarn so formed is taken up by a roll at 900 y.p.m. (823 m.p.m.). The resulting yarn has a denier of 39. The inherent viscosity of the polymer comprising the yarn is 1.58. The yarn is plied (30 ends) at 70 y.p.m. (64 m.p.m.) and the plied yarn is heat-set by passing it (at the same speed) over an 8-inch (20.3 cm.) roll heated to 175 0, contact of the yarn on the roll being maintained over an arc of 180. The plied yarn is then padded with a 5% aqueous anionic textile finishing agent, the pick-up of finishing agent on the yarn being about 1%, after which a tow sheet of 23 plied yarns is formed and fed into the stuffer box crim'per and crimped (8 crimps per inch or about 3 crimps per cm.). The filaments in the crimped tow have a tenacity of 3.8 g.p.d., an elongation of 59%, a modulus of 28 g.p.d., a work recovery of 69% at 5% elongation, and a tensile recovery of 86% at 5% elongation. The tow is skeined and cut to 1.5 inch (3.81 cm.) staple.

In a series of runs, the polypivalolactone staple fibers are blended in various ratios with cotton'fibers and with rayon fibers, following which yarns and fabrics are produced by conventional methods from the staple fiber blends and are compared with each other and with control yarns and fabrics.

The cotton fibers employed in the various runs, with the exception described below, are combed peeler cotton (good middling grade). It is observed that 50% of the fibers are 1.25 inches (3.17 cm.) in length or longer.

The rayon fibers employed in the various runs are standard, 1.5 denier rayon staple having a cut length of 1%; inches (3.97 cm.) (standard Avisco XL produced by the American Viscose Corporation as Style 2301).

The 80% polypivalolactone fiber/20% cotton blend is made with different fiber samples than those described above. The extruded polypivalolactone filaments are quenched with room temperature air flowing radially inward toward the spinneret. The spinning speed is 500 y.p.m. (457 m.p.1n.), and the yarn is after-drawn 3.77 following which it is relaxed at C. for 5 minutes. The yarn has a spontaneous crimp of 7 crimps per inch (2.75 crimps per cm.), an inherent viscosity of 1.5, a tenacity of 2.4 g.p.d., an elongation of 71%, a modulus of 20 g.p.d., and a work recovery of 80%. The fiber cut length is 1.5 inch (3.81 cm.). The cotton fibers employed in this run are combed El Paso cotton (middling grade). It is observed that 50% of the cotton fibers are 1%; inches (2.86 cm.) in length or longer.

In each run, a picker blend totalling five pounds (2.27 kg.) is made, employing as starting materials the weights of the various fibers required to give the weight percentages indicated in the table. The picker lap is carded into sliver, drawn, and converted into roving. The roving is spun into a 40s cotton count yarn. The yarn is woven into a plain weave fabric having a loom construction of 96 sley x 56 picks per inch (38 X 22 per c1n.). The fabrics are finished by scouring, vacuuming to remove water, drying at 250 F. (121 C.), heat setting the dried fabric for 3 minutes at an oven temperature of 375 F. C.), brushed and sheared on both sides, bleached with 0.015% sodium chlorite solution, vacuumed, and dried at 121 C. The fabrics containing cotton have a finished Weight of 3.05:0.25 0z./yd. (104:9 g./m. in each instance while the fabrics containing rayon have a finished weight of 35:04 oz./yd. (119:14 g./m.

The fabrics are evaluated for wash-wear performance by washing them in a home model washing machine using water at 35-38" C. with a commercially available detergent for home laundry use, rinsing the fabric in water at 35-38 C., spin drying, and then hanging in a still atmosphere until fully dry (216 hours). The fabrics are then evaluated by a group of persons on an arbitrary subjective scale using the following ratings:

5 represents a perfectly fiat fabric, no wrinkling or muss 4 represents a fabric deviating only slightly from fiat,

slight wrinkling or muss 3 represents a fabric acceptable for wearing without ironing, having only moderate wrinkling 2 represents a fabric or borderline acceptability for wearing without ironing, easily touched up 1 represents a fabric unacceptably wrinkled for wearing without ironing The fabrics are washed, dried, and rated five times. The average ratings determined in this way are shown in Table 3. Particularly surprising is the enhanced performance of cellulosic fibers having relatively small amounts, i.e. 50% by weight and less, of polypivalolactone fibers blended with them.

The wash-wear performance of fabrics of polypivalolactone fiber/cellulosic fiber blends in highly superior to that obtained with commercially employed polyethylene terephthalate fiber/cellulosic fiber blends. Fabrics similar to those described above were made from blends of polyethylene terephthalate and rayon and cotton, respectively, which were prepared as follows:

The polyethylene terephthalate fibers employed in making the 65% polyethylene terephthalate/35% rayon blend are standard, 1.5 denier, semidull, normal tenacity polyethylene terephthalate staple having a cut length of 1.5 inches (3.81 cm.) (standard polyethylene terephthalate staple produced by E. I. du P-ont de Nemours & Company, Inc. as Type 54). The polyethylene terephthalate fibers employed in making the 65 polyethylene terephthalate/ 35% cotton blend are standard 1.5 denier, semidull, pill resistant polyethylene terephthalate staple designed for blends with cotton and having a cut length of 1.5 inches (3.81 cm.) (polyethylene terephthalate staple for blends with cotton produced by E. I. du Pont de Nemours & Company, Inc. as type 35). The wash-wear rating for the fabrics of the cotton-containing blend was 1.5 while that of the rayon staple-containing blend was 1.7.

TABLE 3.WAS]E[-WEAR PERFORMANCE OF FABRICS [Blends of cellulosic fibers with polypivalolactone staple fibers] Amount of Polypivalolactone Fiber in Wash-Wear Rating Blend, Percent;

Cotton Rayon umoumoawo The 100% citton fabric in the above series has a bulk of 2.7 cc./g., and it is observed that the fabrics of all of the cotton/polypivalolactone staple fiber blends exhibit comparable or superior bulk, ranging from 2.6 to 2.9 cc./g. This is in contrast to the fabric of cotton/polyethylene terephthalate staple fiber blend, which exhibits a relatively poorer bulk of only 2.3 cc./g. although the fabric weight is identical. Similarly, the 100% rayon fabric has a bulk of 2.3 cc./ g. and the rayon/polypivalolactone staple fiber blends exhibit comparable bulk, ranging from 2.3 to 2.5 cc./g., while the fabric of rayon/ polyethylene terephthalate staple fiber blend exhibits a relatively poorer bulk of only 2.1 cc./ g.

A three-component blend is prepared, employing 30% of the polypivalolactone fibers, 60% combed Peeler cotton fibers, and 10% standard, 2.3 denier, polyhexamethylene adipamide staple fibers having a cut length of 1 /2 inches (3.81 cm.) (standard polyhexamethylene adipamide staple produced by E. I. du Pont de Nemours & Company, Inc. as Type 420). Fabric produced as described above from this blend has a Wash-wear rating of 2.1. The weight of the fabric is 3.26 oz./yd. (111 g./m. and its bulk is 3.1 cc./ g. A similar three-component blend prepared from polypivalolactone fibers, 70% combed Peeler cotton fibers, and 10% polyhexamethylene adipamide fibers is worked up into a fabric exhibiting a wash-wear rating of 1.6. Its weight is 3.50 oz./yd. (119 g./1n. and its bulk is 2.36 cc./g.

The wash-wear performance of a fabric depends upon three important factors: the nature of the constituent fibers, the construction of the fabric, and the laundering conditions. In the example above the evaluation of the various fibers and blends thereof in a plain weave fabric is shown since the plain weave construction is one of the most difficult in which to attain adequate wash-wear performance and represents a severe test of the fibers. A change of the fabric construction to any of the various twills results in correspondingly higher wash-wear ratings for each of the fibers and blends thereof. Similarly, the laundering conditions employed in the example represent a severe test, corresponding to laundering in a home with no automatic dryer available and the clothes hung indoors. When the fabrics made of the 40/60 and /35 polypivalolactone/ cotton blends shown in the table are washed as described in the example but tumble dried at C. in an automatic dryer and allowed to hang 2 hours, they are evaluated as having wash-wear ratings of 2.8 and 3.0, respectively, using the same rating system described in the example. Similarly, when the fabrics made of the 40/60 and 65/35 polypivalolactone/rayon blends shown in the table are tumble dried at 70 C. rather than hung in a still atmosphere, they are evaluated as having wash-wear ratings of 3.3 and 3.4, respectively.

What is claimel is:

1. A blend of from about 20 to 95% by weight of cellulosic staple fibers and from about 5 to by weight of polypivalolactone staple fibers, said blend having high compressional recovery.

2. The blend of claim 1 wherein the cellulosic fibers are cotton.

3. The blend of claim 1 wherein the cellulosic fibers are rayon.

4. A blend of from about 50 to by weight of cellulosic staple fibers and from about 5 to 50% by weight of polypivalolactone staple fibers, said blend having high compressional recovery.

5. The blend of claim 4 wherein the cellulosic fibers are cotton.

6. The blend of claim 4 wherein the cellulosic fibers are rayon.

7. A yarn containing a blend of from about 20 to about 95% by weight of cellulosic staple fibers and from about 5 to 80% by weight of polypivalolactone staple fibers.

8. A yarn containing a blend of from about 50 to 95 by weight of cellulosic staple fibers and from about 5 to 50% by weight of polypivalolactone staple fibers.

9. A wash-wear fabric of yarn according to claim 8.

References Cited UNITED STATES PATENTS 2,658,055 11/1953 Alderson 260-783 2,701,406 2/1955 B10014 57l40 2,745,240 5/1956 Brant 57l40 2,887,468 5/ 1959 Caldwell ct al. 26078.3 X 2,897,042 7/1959 Heiks 57l40 X 2,985,940 5/1961 Weldon.

3,016,683 1/1962 Simpson 57l40 3,044,250 7/1962 Hebeler 57l40 3,299,171 1/1967 Knobloch ct al 57144 X FOREIGN PATENTS 766,347 1/1957 Great Britain.

JOHN PETRAKES, Primary Examiner. 

